Oxidation catalysis - electronic theory revisited

Transfer of electrons between reacting molecules and solid oxide catalysts is shown to be a much more complex phenomenon than assumed in the electronic theory of catalysis. Interface electron transfer requires matching energy and symmetry of frontier orbitals; therefore the energy levels of the reacting molecule must correspond to the region of high density of states of the solid. This can be achieved either by activation of adsorbing molecule or through generation of defects, introduction of dopants, or deposition of the active phase on a support to form oxide-monolayer-type catalysts. An example of the interaction of methane and V2O5 with various defects is discussed. It is shown that the cleavage of the C-H bond in primary carbon proceeds by transfer of two electrons to the empty vanadium surface levels and formation of adsorbed alkoxy and surface hydroxyl species. (C) 2003 Elsevier Science (USA). All rights reserved.